This invention relates generally to systems for expressing fluids and liquids from fibrous materials, and more particularly, to a continuous feed system having improved and simplified structure and dynamic adjustability.
The purpose of an expressing system for fibrous material is to extract a maximum amount of fluid from fibrous material passing under pressure therethrough. The percentage of fluids remaining in the fibrous material exiting such a system is a most pertinent gage for system efficiency.
Screw presses are typically used to express oils, liquids or fluids from fibrous materials such as sugar cane, sludges, and the like. These screw press systems include a main body or housing with drainage openings through the housing side walls and a feed worm connected onto a main shaft which is rotationally driven within the cage to compress the fubrous material as it is fed through such systems. Two such systems are described in my previous U.S. Pat. Nos. 4,440,076 and 4,644,861; other older screw press systems are described in the prior art cited in each of those two patents.
Several operational limitations may exist in conjunction with these well-known screw presses, especially those serving as the single dewatering operation. One such limitation is the inability to effectively vary the fluid slots between the cage of drainage bars which form the housing during system operation. This variability would enhance the operating efficiency of such systems.
In dewatering some fibrous materials such as paper sludge which contain a considerable amount of liquids, a common practice is to introduce a polymer into the fibrous material to facilitate the dewatering process. The efficiency of the expressing process is enhanced when the fibrous material is not churned or mixed during the expressing. Thus, conventional screw presses which do, in fact, force the fibrous materials through the expressing chamber while exerting considerable amount of disruptive forces as the material is expressed are not effective for expressing such polymerized slurrys during the initial free drainage periods.
The present invention is directed to a considerably simpler form of unique structure which is particularly adaptable to more heavily watered fibrous material and/or those in slurry form. The present system provides structure which, in one general embodiment, eliminates all internal moving parts thereby substantially reducing churning, maintenance costs, as well as the cost of manufacture and replacement components. Additionally, the preferred embodiment of the present system is adaptable to serve as a first, intermediate, or final stage of expressing fibrous materials in conjunction with the abovedescribed and/or other conventional dewatering means. In dewatering, some fibrous materials such as paper sludge, it is not always possible to obtain feed stock with consistent physical properties. Feed stock processing fibers with a short fiber length require drainage slots of smaller dimension while other feed stocks with longer fiber lengths will be contained within the compression chamber by larger drainage slots. Inherent in this invention is an adjustable means for dynamically varying the drainage slot while the system is operating to obtain the optimum drainage of liquid while containing the solids, for both the novel and preferred drainage system and conventional screw presses.